New data on the reproductive biology of the thorny stingray,Dasyatis centroura (pisces: Dasyatidae) from off the Tunisian coasts

Synopsis Aspects of the reproductive biology are described for the thorny stingray,Dasyatis centroura, caught off the coasts of Tunis, mainly from the Gulfs of Gabes and Tunis. Sexual maturity in males occurs at a disk width (DW) of 800 mm. Female maturation occurs between 660 mm and 1000mm DW All males and females having a DW greater than 800 and 1000mm, respectively, were adults. Females are larger than males, with adult specimens having an average DW of 1040mm in males and 1345mm in females. Gestation lasts for a minimum of about 4 months. The number of reproductive cycles per year is unknown. Vitellogenesis is completed at the end of the gestation. Parturition and ovulation occur in June. Fecundity ranges from 2 to 6 individuals per litter.     

A new method for measuring growth and age in the precious red coral<Emphasis Type="Italic"> Corallium rubrum</Emphasis> (L.)

A new technique for aging red coral Corallium rubrum (L.) colonies based on staining the organic matrix found in the axial calcareous skeleton is presented and validated. This method provided clear-cut images of growth rings of red coral. To demonstrate their annual periodicity, two approaches have been used: (i) applying this technique to adult colonies of known age (more than 20 years old), and (ii) labeling colonies with calcein and allowing them to grow for 1 year. Results provided evidence of the annual periodicity of growth rings. This new method assesses colony age with an underestimate of true age by 3–4 years. The difference between estimated age and actual age could be attributed to the phase of initial growth during which rings are not formed. Colonies from different sites, depths, and habitats (n=33) were analyzed yielding preliminary data on longevity and mean growth rates in red coral. Colonies from shallow habitats (15–62 m) examined here with basal diameter of about 7 mm were at least 30–40 years old. Mean growth rate of basal diameter was 0.35±0.15 mm year^–1. Comparison with previous aging methods used for red coral resulted in considerable differences in estimations of age (about 10 years greater in this study) and growth rates (about four times lower). The application of this method to red coral will provide key data as a basis for developing management and conservation plans for this valuable species.Communicated by: H.R. Lasker     

Leg impairment affects the reproductive attributes of a ladybird,Menochilus sexmaculatus (Fabricius)

Natural injuries and their causes have recently garnered attention amongst researchers, however the effects of these injuries on life history traits are still sparsely investigated. In the few studies that have been conducted injuries are known to have a debilitating effect on male virility and reproductive performance. Thus the effect of leg injuries in males on mating behaviour and reproductive output in the ladybird beetle, Menochilus sexmaculatus was investigated. This is the first study on the effect of injury on any life history trait in Coccinellidae. The legs of the male were amputated at three different joints on the same side and opposite sides for one leg or two legs. These amputated males were paired with uninjured females and the mating behaviour and subsequent reproductive output was observed. Time to commence mating, latent period and mating duration in impaired males were observed and were all found to be higher than that of uninjured males. Fecundity and percent egg viability were reduced in all impaired male pairs. Males with physical disability were found to copulate for an extended duration, perhaps to ensure maximum paternity.     

Microendoliths in Lower Pliocene Oysters from the Alt Empordà Basin,NW Mediterranean: Paleoenvironmental Inferences

The study of traces made by microendoliths on Neopycnodonte cochlear shells from a coquina in the Vilacolum area (Alt Empordà basin) has permitted us to identify for the first time 18 ichnotaxa in the Lower Pliocene sediments of the NW Mediterranean. A shallow, euphotic environment with local shaded zones (corresponding to deep shallow conditions) is proposed for this shell bed, owing to the presence of abundant heterotroph microborings and rare cyanobacterial traces as well as to the high number of Rhopalia catenata and Ichnoreticulina elegans. This refines a former interpretation, mainly based on body fossils and macroborings, which suggested simply a shallow depositional environment. The ichnospecies Ichnoreticulina elegans, Rhopalia catenata, ?R. clavigera, Saccomorpha clava, S. terminalis, Polyactina araneola, Entobia mikra, Orthogonum lineare and Aurimorpha varia are identified for the first time in marine Pliocene materials, thus furnishing a more complete picture of the temporal span of some microborers.     

太行花生殖生物学研究Ⅱ有性生殖与无性生殖的调查与研究

通过原产地调查,引种试验,扦插及种子萌发等实验,研究了太行花的繁殖及扩散方式。结果表明,太行花有两条生殖途径：一条是有性生殖;另一条是无性生殖。在原产地因生境条件特殊,有性生殖能力弱,主要靠无性生殖扩大种群。在北京人工栽培条件下,两种生殖方式都能正常进行。     

THE EVOLUTION OF REPRODUCTIVE EFFORT IN LIZARDS AND SNAKES

Life history theory suggests that the optimal evolved level of reproductive effort (RE) for an organism depends upon the degree to which additional current reproductive investment reduces future reproductive output. Future reproduction can be decreased in two ways, through (i) decreases in the organism's survival rate, and/or (ii) decreases in the organism's growth (and hence subsequent fecundity). The latter tradeoff–that is, the “potential fecundity cost”—should affect the evolution of RE only in species with relatively high survival rate, a relatively high rate of fecundity increase with body size, or a relatively high reproductive frequency per annum. Unless these conditions are met, the probable benefit in future fecundity obtained from decreasing present reproductive output is too low for natural selection to favor any reduction in RE below the maximum physiologically possible. Published data on survival rate, reproductive frequency and relative clutch mass (RCM) suggest that many lizard species fall well below the level at which natural selection can be expected to influence RE through such “potential fecundity” tradeoffs. Hence, the relative allocation of resources between growth and reproduction is unlikely to be directly optimized by natural selection in these animals. Instead, energy allocation should influence the evolution of RE only indirectly, via effects on an organism's probability of survival during reproduction. Survival costs of reproduction may be the most important evolutionary determinants of RE in many reptiles, and information on the nature and extent of such costs is needed before valid measures of reptilian RE can be constructed.     

Spawning and distribution of bluefish Pomatomus saltatrix (L.) in the northwestern Mediterranean

The present study was carried out on the Catalan coast, the northern limit of the geographic distribution of Pomatomus saltatrix (Linnaeus, 1766) in the Mediterranean. Within the area studied, both larvae and adults were more abundant in the southern part, where surface temperature was slightly higher than in the north. Spawning of P. saltatrix was limited to the warmest months, from July to September, when the surface temperature was about 25° C, The most common larval sizes, between 2.25 and 2.75 mm s.l. , were distributed over the continental shelf, and the greatest concentrations were found between 20 and 100 m, suggesting an inshore spawning. Larvae, including the smallest sizes, were found in the most superficial layers and no evidence of vertical migration was observed. The species was regularly fished in the southern zone, maximum monthly catches ranging between 10–20 tonnes. The presence of adults in the coastal zone showed a marked seasonality closely related to temperatur, the lowest catches corresponding to the coldest months.     

Reproduction of macrourids in the upper slope of the north-western Ionian Sea

Aspects of reproduction of macrourid fish in the north-western Ionian Sea are reported. Data were collected during 12 trawl surveys carried out between 1993 and 1995. Mature and running ripe females of Coelorhynchus coelorhynchus, Hymenocephalus italiens and Nezumia sclerorhynchus were found all year round. Mature females of Trachyrhynchus trachyrhynchus were found mainly in August.     

The evolution of gynodioecy on a lattice

Gynodioecy is a breeding system in plants where populations consist of hermaphrodites and females. The females result from a genetic mutation which impairs pollen production in hermaphrodite plants. Most previous models for the evolution of gynodioecy do not take into account any spatial detail, which might be expected to play an important role in populations with short range interactions caused by poor or no locomotion.In this article we present a generalised mean-field analysis (which ignores any spatial detail), together with stochastic spatial simulations, to investigate the spatial effect on the evolution of gynodioecy. We show that, in a population of hermaphrodites where male sterility is caused by a dominant allele in a nuclear gene, mean-field calculations greatly underestimate the reproductive advantage females require to become viable under spatial constraints. This suggests that gynodioecy is less likely to evolve in plants with more localised pollination and seed setting. This may have implications for the evolution of dioecy, a breeding system in plants where the population consists of males and females, as gynodioecy is thought to be a route to dioecy. Our results also demonstrate that a lower frequency of females should be expected for gynodioecious populations when interactions are local. This is relevant when comparing the results of breeding experiments with observations of female frequency in the wild.     

Sexual selection and intelligence: Does sexual reproduction drive the evolution of intelligence?

The basal hypothesis discussed here is the idea that brain architecture could be plastic on a very basal, genetic level due to sexual recombination and reassortment of alleles of genes related to brain development, e.g., neuronal cell adhesion molecules (NCAMs) and others.The role of sexual reassortment leads the study of brain development, species behavior and intelligence to a new version of the so-called “Red Queen Hypothesis”: using the mechanism described here, a kind of runaway selection mechanism seems to arise. Even if NCAMs are almost constant within an individual, they seem to act very differently at the population level and so the role of reassorting polymorphic NCAM- (and other) genes gets particularly clear. If several NCAM-NCAM combinations cause extreme behavior and intelligence variability in a population, these combinations also represent a use of sexual selection. This mechanism of NCAM allele assortment seems to be important for the process of speciation by mutual selection of individuals. Therefore NCAM variants and their associated behaviors are thought to be important for the development of intelligence, in that they promote the attraction of individuals with already high intelligence, leading to the speciation of super-intelligent groups.     

Upper thermal thresholds of shallow vs. deep populations of the precious Mediterranean red coral Corallium rubrum (L.): Assessing the potential effects of warming in the NW Mediterranean

Recent mortality outbreaks in marine ecosystems have been linked to elevated seawater temperatures associated with global climate change. Acquisition of thermotolerance data is essential, not only to determine the role of temperature in mortality outbreaks, but also to predict consequences of global warming. In the NW Mediterranean region, elevated seawater temperatures during the summer periods of 1999 and 2003 caused mass mortality of the Mediterranean red coral, Corallium rubum (L. 1758). Experiments testing the upper thermal limits of this species were carried out in aquaria using samples collected from populations from 11 to 40 m depth in the Marseilles region (NW Mediterranean, France). Samples were subjected to temperature treatments between 18 and 30 °C with an exposure time of 5 and 25 days. Three biological response variables were used to evaluate effects of the treatments: coenenchyme necrosis, polyp activity and calcification rates (⁴⁵Ca incorporation in calcareous skeleton). The results showed that exposure to 24 °C for 24 days caused a beginning of mortality only for the deep population, and to 25 °C for between 9 and 14 days caused mass mortality of both sample groups. The response variable results indicate that samples from the shallow population had greater thermotolerance of elevated seawater temperatures than the deep samples. The shallow samples showed greater polyp activity and higher calcification rate with a delayed necrosis response than the deep samples. These initial thermotolerance results combined with both hydrographic models and seawater temperature monitoring are the first step towards developing predictive tools for anticipating future effects of climate change in the red coral populations.     

Acidification affects the perch,Perca fluviatilis,populations in small lakes,of southern Finland

Synopsis Characteristics of perch were studied in 4 recently acidified lakes in southern Finland. The densities of the populations were 0–250 ha^–1 compared with 1400–3300 ha^–1 in two circumneutral reference lakes. The perch were close to extinction in one acidic lake and dominated by 7 year old fish in two other acidic lakes, suggesting decreased reproduction. Individual fecundity was not reduced by the acidity, but high mortality (close to 100%) of eggs in two acidic lakes indicated recruitment failure. In one of the acidified lakes reproduction had continued resulting in a population dominated by younger fish. However, increased egg mortality, low density, and the resulting high growth rate of perch in this lake were considered to be consequences of the acidity. These findings are the first documentation on the possible decrease of fish populations in Finland due to acid precipitation.     

Sexual reproduction in the arum lily family,with emphasis on thermogenicity

Summary Floral thermogenicity, which is found in several representatives of half a dozen angiosperm families, is most pronounced in the Araceae. It is based on the operation of an alternative, cyanide-resistant electron transport chain which, in contrast to the classic cytochrome oxidase system, produces little ATP; most of the energy originally locked up in the respiratory substrate usually starch — is therefore liberated in the form of heat. The biological function of this (biochemically wasteful) system is to release the heat to serve as a volatilizer for the floral odors (often containing aliphatic amines, indole and skatole) that attract the insect pollinators. This makes the survival value of thermogenesis (for the plant species) immediately clear. Thermogenicity is under tight biological control, as demonstrated by the fact that the same ceiling temperature is always reached, regardless of ambient temperature. In Eastern skunk cabbage (Symplocarpus foetidus), which flowers very early in spring, that ceiling is about 20° C, in tropical forms such as Xanthosoma robustum and Philodendron selloum, it lies in the 42°–44° C range. In several instances, e.g., in Arum and in Sauromatum, the voodoo lily, thermogenicity manifests itself as a flare-up of only a few hours' duration, a respiratory explosion that can lead to rates of metabolism that compare favorably with those of a hovering hummingbird. The metabolic peak is always reached at a particular time of day, which is different for the different arum lily species, and thus reduces competition for pollinators. The odors that accompany the heat are also very characteristic, appealing to different pollinator classes and further reducing such competition. In the voodoo lily and in Arum, the primary site for the production of both heat and odor is the naked appendix of the inflorescence, which acts as a specialized osmophore or odor carrier. The first explosion may be followed by another one several hours later, which manifests itself in the floral chamber of the inflorescence and is under strict photoperiodic control. In Sauromatum, the first metabolic explosion is triggered by a plant hormone, originally referred to as calorigen, which originates in the primordia of the staminate flowers and moves from there into the appendix where it exerts its action after a lag-time of about a day — an indication that synthesis of new enzymatic protein (through unblocking of certain genes?) may well be involved. In 1987, calorigen was shown to be identical with salicylic acid. This compound was already known to induce flowering in certain duck-weeds, Lemnaceae, which until recently were regarded as belonging to the same family as arum lilies. In certain water lilies (Nymphaeaceae), thermogenicity is combined with a pollination syndrome very similar to that of Arum and Sauromatum but involving temporary trap flowers.Dedicated to the memory of A.W.H. van Herk, pioneer in the study of arum lilies, superb lecturer, and unselfish human being     

Sustainability of dioecious and hermaphrodite populations on a lattice

Sexual reproduction may be divided into two main categories: hermaphroditism and dioecy (Botany)/gonochorism (Zoology). Simultaneous hermaphrodites can function in both male and female roles whereas a dioecious/gonochorist population consists of distinct male and female individuals. Mean-field calculations, which ignore spatial aspects, suggest that self-incompatible hermaphrodites should have a twofold advantage over dioecious population when reproduction is limited by mating encounters. By use of stochastic spatial simulations we demonstrate that hermaphroditism has an even greater advantage when local interactions are considered. This result provides further support for the observation that hermaphroditism is associated with sedentary species, such as plants and animals with poor mate search efficiency. We also investigate the finite size effects associated with the well-known quadratic contact process.     

Intraclonal variation in propensity for mixis in several rotifers: variation among females and with maternal age

In 14 previously published experiments with clones of three species of Brachionus, Epiphanes ukera, and Rhinoglena frontalis, females cultured singly in small volumes from birth through most of their reproductive period usually produced some mictic daughters. Here, these data are analyzed to test two hypotheses: the propensity of females in a clone to produce mictic daughters will vary significantly among females, and will decrease with female age. Significant heterogeneity (χ²) among replicate females was demonstrated in two clones of B. calyciflorus from Florida, in single clones of this species from Georgia, Texas, Spain, and Australia, in a clone of B. angularis from Argentina, and in single clones of E. ukera and R. frontalis from Germany. No significant heterogeneity was found in two other clones of B. calyciflorus from Florida and in a clone of B. variabilis from Spain. Significant heterogeneity among females of a clone could be caused by chance fluctuations during development, differences in birth order, or epimutations. This heterogeneity is an important component of a bet-hedging strategy to balance production of diapausing fertilized eggs and future population growth by female parthenogenesis. The propensity of a female to produce mictic daughters did not decrease with her age. In experiments with six different clones from four strains of B. calyciflorus, and with single clones of E. ukera and R. frontalis, only one clone of B. calyciflorus showed significant variation (ANOVA) in the proportion of mictic daughters produced in three or four successive one- or two-day periods. In this clone the proportion of mictic daughters increased with maternal age. Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez Advances in Rotifer research